In a typical prior art magnetic disk recording system a slider containing magnetic transducers for reading and writing magnetic transitions flies above the disk while it is being rotated by a spindle motor. The disk includes a plurality of thin films and at least one ferromagnetic thin film in which the recording (write) head records the magnetic transitions in which information is encoded. The magnetic domains in the media on can be written longitudinally or perpendicularly. Perpendicular magnetic recording is considered to be superior to longitudinal magnetic recording for ultra-high density magnetic recording. The increase demand for higher areal density has correspondingly led to increase demand to explore ways to reduce the width of the write pole piece, increase the write field strength, and improve the write field gradient.
In a disk drive using perpendicular recording the recording head is designed to direct magnetic flux through the recording layer in a direction which is generally perpendicular to the plane of the disk. Typically the disk for perpendicular recording has a hard magnetic recording layer and a magnetically soft underlayer. During recording operations using a single-pole type head, magnetic flux is directed from the main pole of the recording head perpendicularly through the hard magnetic recording layer, then into the plane of the soft underlayer and back to the return pole in the recording head. The area of the main pole piece facing the air-bearing surface is designed to be much smaller than the area of the return pole piece. The shape and size of the main pole and any shields are the primary factors in determining the track width. FIG. 1 illustrates a prior art disk drive 13 with a head 26 for perpendicular recording and the associated magnetic recording media 27. The conventional. The write head is inductive and includes a coil 45 and pole pieces 41, 42, 43 and 44 with the main pole piece 42 having a pole piece tip 42T. The section taken is perpendicular to the air-bearing surface. FIG. 2 is an illustration of an ABS view of the recording head 26 showing an enlarged view of the pole piece tip 42T as viewed from the air-bearing surface. The read and write elements of the head (also called a slider) are built-up in layers on a wafer using thin film processing techniques to form a large number of heads at the same time. Conventionally after the basic structures for the heads have been formed the individual heads rows of heads) are cut from the wafer to expose what will become the air-bearing surface after further processing. The processing of the air-bearing surface typically includes lapping and formation of air-bearing features typically called rails. The air-bearing features separate the active components of the head such as the pole piece tip 46 from the air-bearing surface which is further separated from the media by an air gap.
In published U.S. patent application 2003/0223150 by Edward Lee a method of protecting the front P2 pole tip during the ion mill patterning of the yoke is described. A front connecting pedestal is electroplated over the front P2 pole tip slightly behind the ABS, and a back gap connecting pedestal is electroplated over the back gap P2 pedestal. Insulator materials are formed over the front P2 pole tip, over the front connecting pedestal, and in between the front and the back gap connecting pedestals. Next, a chemical-mechanical polishing (CMP) is performed over the top of the structure to form a substantially planar top surface. A full-film of yoke layer materials is then sputter deposited over this top surface, followed by the formation of a photoresist mask slightly behind the ABS. When the yoke layer materials are subsequently ion milled to form the yoke, the front P2 pole tip is protected by the surrounding insulator. The front and back gap connecting pedestals form an intervening magnetic layer which connects the front P2 pole tip and back gap P2 pedestal to the yoke.
In published U.S. patent application 20030137771 by Hugo Santini a method of ion milling pole tips in a longitudinal write head is described. Photoresist is spun patterned to form a mask for ion milling to notch the bottom first pole tip layer adjacent first and second side edges of the top first pole tip layer. The use of the ZTH defining layer protects the top surface of the bottom first pole piece layer from thinning due to ion milling except at the notches. It can be seen from the drawings that the ZTH defining layer has set in motion notches for the bottom first pole piece layer without reducing the thickness of the bottom first pole piece layer in first and second field locations outwardly from the notches.
Ion-milling of a pole piece tip for perpendicular heads is advantageous to produce a trapezoidal shape for the pole piece tip. Producing the ion-milling mask is problematic under the current art, since it involves using RIE on an alumina layer. RIE of alumina requires chlorine based chemistry which is expensive and involves inherent safety problems. Polyimide ion-milling masks can also be used, but they are difficult to manufacture with a sufficiently high aspect ratio and the required precision is difficult to achieve. Electroplated ion-milling masks have insufficient milling resistance and dimension control is problematic. A safer and less expensive method of fabricating of pole piece tips is needed.